Description of problem:

While attempting to remove a large writecache LV (1TB) from a VG, the system crashed
due to Out-Of-Memory.

My system actually has 32GiB RAM, and I was playing with a 1TB size writecache

Version-Release number of selected component (if applicable):

RHEL 8.6

How reproducible:

Always

Steps to Reproduce:

• Add a large device as a writecache to a VG:
  #lvconvert --type writecache --cachevol fast vg/main

• Attempt to remove it from the VG with lvconvert --uncache (or split cache)

Actual results:
System crashes and enters in an unrecoverable state even if the volume isn't mounted automatically. During boot, lvm spends a long time trying to scan the device with the large cache, and the system fails to boot because it starts to throw OOM errors before finishing to boot.

Expected results:

• LVM prevents a large device to be added as a writecache if the system has not enough memory to deal with it.

• System shouldn't crash while removing a cache from the VG.
  If a system has been using a cache device, but for some reason the total RAM has to be reduced, this shouldn't cause a crash while removing the cache device from the volume group.

Additional info:

I managed to boot in recovery mode, but any attempt to remove the writecache device from the VG failed. The system was unable to remove it and crashed.

I manage to manually remove the writecache device from the VG by hacking the current VG configuration file, removing the writecache from it, and restoring the configuration without the writecache device by using vgrestore.